R75/6 DOA - Electrical woes...can you help?

[mattyG]

I have an R75/6 that's got an electrical gremlin I'm trying to sort out. I tried to jump it last year off a car battery and it almost caught and then went dark (no idiot lights, nothing) and some smoke started coming out from under the tank. That freaked me out so I shelved it for awhile. I'm trying to sort it out now. The battery won't take a charge so I'm going to get a new one. I poked around under the tank and I couldn't find any obvious wiring issues. I opened the front cover and the red lead going into the diode board was a little funky looking (maybe partially melted?) so I redid the connection. The starter relay looks OK externally. I connected the bike back up to my car battery and the faint illumination lights in the aspersions light up when I turn the key on but nothing else. The run switch does nothing. Not sure where to go...does anyone have suggestions?

[Rob]

If possible, I would open the starter relay to check out the internals.
You may have overheated it.
At the very least, test it with a VOM to make sure the contacts are open with no power, and closed when you apply 12 v to the other contacts.
You should also hear a click when power is applied.

My money is on fried relay.

If the bike doesn't start after several short tries, don't just keep cranking with an inexhaustible power source. Find the problem. You are just going to create more problems. You will be lucky not to have damaged the starter.

[mattyG]

Yeah, I hope its the relay and not the starter. There is no click when power is applied that I can hear.

[Rob]

If you own an airhead, you need a volt-ohm meter.

[richard t]

check for loose connections, as well as what Rob suggested

[Airbear]

G'day mattyG, and welcome to the forum.
I've been following your thread on ADV and it seems you are getting pretty good advice there. Last I read was that Wirespokes suggested you check Snowbum's site for info on the starter relay. Here is the article he means:

http://bmwmotorcycletech.info/startingprobs.htm

Best of luck wading through that. It is good info, just hard to find exactly what you need.

Your 1976 /6 has all the nasty complications in the starting circuits. A kill switch, the clutch switch working in conjunction with the neutral switch and there's the dreaded Light Relay. Any little problem with any of those bits and your bike is not going to start.

It is almost impossible for anyone to help at a distance. You need to use a wiring diagram and a test light or multimeter, go over every connection, test every switch and continuity of wires.

Best advice is to start with the simple things first. You need a new battery first from what I've read. I'd be fitting that but make sure you can detach the negative lead quickly. I like to cut a slot in the ring connector, like this:



Check the two fuses in the headlight - if they are good, give them a twist in their holders to make sure they are connecting properly. Pull the starter relay (take pictures and/or draw diagram of connections first) and check operation. Google up some info if you are new to relays, connect power to the pins that make it work and check that the contacts actually work to switch power to the solenoid.

Sadly there is no silver bullet. It is thoughtful methodical work that will solve your problem. I see you are in Seattle - there is a mob of airhead owners there, even a club of some sort IIRC. That is bound to be a useful resource.

Best of luck attached.

[Texer]

Great points by Airbear. I had issues with wiring last year on my /6, I theeeeenk mostly solved. I live in Seattle as well. Feel free to pm me if you'd like to chat.